Add cap and builder feature for multisample interpolation

src/gpu/glsl/GrGLSLFragmentShaderBuilder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLSLFragmentShaderBuilder.h"
 #include "GrRenderTarget.h"
 #include "gl/GrGLGpu.h"
@@ skipping 69 matching lines @@
     fUsedProcessorFeatures = GrProcessor::kNone_RequiredFeatures;
     fHasReadDstColor = false;
 #endif
 }
 
 bool GrGLSLFragmentShaderBuilder::hasFragmentPosition() const {
     return 0 != fProgramBuilder->header().fFragPosKey;
 }
 
 bool GrGLSLFragmentShaderBuilder::enableFeature(GLSLFeature feature) {
+    const GrGLSLCaps& glslCaps = *fProgramBuilder->glslCaps();
     switch (feature) {
-        case kStandardDerivatives_GLSLFeature: {
-            if (!fProgramBuilder->glslCaps()->shaderDerivativeSupport()) {
+        case kStandardDerivatives_GLSLFeature:
+            if (!glslCaps.shaderDerivativeSupport()) {
                 return false;
             }
-            const char* extension = fProgramBuilder->glslCaps()->shaderDerivativeExtensionString();
-            if (extension) {
+            if (const char* extension = glslCaps.shaderDerivativeExtensionString()) {
                 this->addFeature(1 << kStandardDerivatives_GLSLFeature, extension);
             }
             return true;
-        }
-        case kPixelLocalStorage_GLSLFeature: {
-            if (fProgramBuilder->glslCaps()->pixelLocalStorageSize() <= 0) {
+        case kPixelLocalStorage_GLSLFeature:
+            if (glslCaps.pixelLocalStorageSize() <= 0) {
                 return false;
             }
             this->addFeature(1 << kPixelLocalStorage_GLSLFeature,
                              "GL_EXT_shader_pixel_local_storage");
             return true;
-        }
+        case kMultisampleInterpolation_GLSLFeature:
+            if (!glslCaps.multisampleInterpolationSupport()) {
+                return false;
+            }
+            if (const char* extension = glslCaps.multisampleInterpolationExtensionString()) {
+                this->addFeature(1 << kMultisampleInterpolation_GLSLFeature, extension);
+            }
+            return true;
         default:
             SkFAIL("Unexpected GLSLFeature requested.");
             return false;
     }
 }
 
 SkString GrGLSLFragmentShaderBuilder::ensureFSCoords2D(const GrGLSLTransformedCoordsArray& coords,
                                                        int index) {
     if (kVec3f_GrSLType != coords[index].getType()) {
         SkASSERT(kVec2f_GrSLType == coords[index].getType());
@@ skipping 205 matching lines @@
 }
 
 void GrGLSLFragmentShaderBuilder::onAfterChildProcEmitCode() {
     SkASSERT(fSubstageIndices.count() >= 2);
     fSubstageIndices.pop_back();
     fSubstageIndices.back()++;
     int removeAt = fMangleString.findLastOf('_');
     fMangleString.remove(removeAt, fMangleString.size() - removeAt);
 }